1. Field of the Invention
The present invention relates to an illumination apparatus and a photographing apparatus having the same.
2. Related Background Art
In recent years, in order to make the photographing possible in a situation in which the sufficient exposure is not obtained as in the photographing at night or in the photographing in shade, an artificial illumination apparatus is used in an optical photographing apparatus typified by a digital camera. As for the optical photographing apparatus including such the illumination apparatus, for example, there are known one mounting an illumination apparatus having an LED as a light source for emitting stationary light for photographing of a moving picture, and one mounting a stroboscope which has been frequently used in order to photograph a still image.
Many illumination apparatuses of this sort normally cover a photographing distance range of about 50 cm to about 3 m as normal photographing distances. Thus, each of them is adjusted so as to have the light distribution characteristics suitable for such the distance.
On the other hand, in recent digital cameras, the number of photographing apparatuses is increasing each of which can photograph even at the very short distance, e.g., even at close range of about several centimeters from a photographing lens.
If the illumination apparatus adopting the conventional system is used under such circumstances, in particular, in the photographing at close range, the sufficient characteristics cannot be obtained in terms of the illuminating light. That is, a part of the illuminating light is blocked off by a photographing lens barrel, and hence the whole necessary surface to be illuminated cannot be uniformly illuminated by the illuminating light in some cases. In addition, since a distance to a subject is very short, the exposure for the subject becomes overexposed, and hence the preferable illumination state cannot be obtained in some cases.
For the purpose of avoiding such conditions, in order to make it possible to illuminate corresponding to a subject which is in a short distance away from a photographing apparatus, a large number of illumination apparatuses dedicated to the proximity photographing have been proposed to be commercialized. For example, a stroboscope for macro photographing is generally well known in which a ring-like slender light source is disposed at the head of a photographing lens barrel in order to previously prevent an unbalanced dark shadow from being generated at the back of a subject. However, since such a stroboscope is very expensive, it is difficult to install the stroboscopes in all the optical photographing apparatus.
In addition, recently, an illumination apparatus using a light emitting diode (LED) as a simplified illumination light source for a video camera is installed in a main body of an optical photographing apparatus. The illumination apparatus using a light source such as an LED shows its effect under the very dark situation to which the outside light is hardly applied. However, since similarly to the case of the illumination using the above-mentioned stroboscope, the eclipse by the photographing lens barrel may occur in some cases, it may not safely be said that such an illumination apparatus is an illumination optical system suitable for the short distance photographing.
As described above, it is very difficult to carry out the illumination suitable for both the normal photographing and the short distance photographing (macro photographing) with an illumination apparatus mounted in a small space given to the optical photographing apparatus. Actually, however, the illumination apparatus is required to be suitable for both the normal photographing and the short distance photographing, and there is desired the appearance of the illumination optical system which fulfills the illumination corresponding to such individual photographing states, and which can be inexpensively configured.
Then, in order to respond to the above-mentioned demand, an illumination apparatus is proposed in which fibers for guiding fluxes emitted from a light source to the circumference of a photographing lens are disposed in a ring-like shape, and the light emitted from the fibers is used for illumination light (see Japanese Patent Application Laid-Open No. 2000-314908 for example). In addition, an illumination apparatus is proposed which is switchable between two states, one state being a normal stroboscopic photographing state, and the other state being a state in which light beams are guided to a light guide portion for guiding the light emitted from a flash light emitting portion to a plane of projection in the periphery of a photographing lens barrel portion (refer to Japanese Patent Application Laid-Open No. H08-043887 for example). Moreover, a stroboscopic apparatus is proposed which is configured so that the stroboscopic apparatus is mountable on a camera and has such a ring-like portion as to surround a photographing lens barrel of the camera, and strobe light is guided in a circumferential direction of the ring-like portion, and then the light reflected by a reflecting surface of the ring-like portion is emitted through an emission surface facing the reflecting surface (see Japanese Patent Application Laid-Open No. 2001-255574 for example).
However, in the case of the above-mentioned illumination apparatus using the fibers, it is necessary to use a large number of fibers, and hence the product cost increases. In addition, though the emission positions of the light beams can be uniformly arranged in the peripheral portion of the photographing lens barrel, the light distribution characteristics cannot be controlled. Hence, it can be a high possibility that the illumination apparatus concerned becomes an apparatus having the light distribution characteristics having a range wider than an actually required irradiation range.
In addition, with respect to the above-mentioned illumination apparatus in which optical path thereof is selectable between the two states, i.e., the normal stroboscopic photographing state, and the state in which light beams are guided to the light guide portion for guiding the light emitted from the flash light emitting portion to the plane of projection in the periphery of the photographing lens barrel portion, for example, it is conceivable that there is adopted an optical system in which a diffusion surface having a predetermined distribution is formed on a side opposite to the emission surface of the ring-like member as being frequently used in a back light illumination optical system, and a quantity of light emitted through the emission surface is uniformized based on the distribution of the diffusion surface. Since in such an optical system, the diffusion surface is interposed, it is difficult to construct the illumination optical system which is excellent in efficiency.
Moreover, the above-mentioned stroboscopic apparatus is configured so that the light beams are guided from the light source to the ring-like light guide member and emitted through the emission surface. However, the light beams are taken in the ring-like light guide member from both the directions of the ring-like light guide member, and also the shape of the reflecting surface of the ring-like light guide member is formed in the form of an intermittent prism surface in which the density gradually changes. Hence, only a specific angle light component incident on the ring-like light guide member at a specific angle is effectively utilized. As a result, it is difficult to configure the illumination optical system having the excellent efficiency.